from datetime import datetime
from . import db, scheduler
from .models import Job
import docker
import json
import os


def checkout_jobs():
    with scheduler.app.app_context():
        client = docker.from_env()
        jobs = db.session.query(Job)
        for job in jobs.filter_by(status='submitted').all():
            _command = (job.service
                        + ' -i /files'
                        + ' -o /files/output'
                        + ' ' + ' '.join(json.loads(job.service_args)))
            _constraints = ['node.role==worker']
            _image = 'gitlab.ub.uni-bielefeld.de:4567/sfb1288inf/{}:{}'.format(
                job.service,
                job.service_version
            )
            _labels = {'service': job.service}
            _mounts = [os.path.join('/home/compute/mnt/opaque',
                                    str(job.user_id),
                                    'jobs',
                                    str(job.id))
                       + ':/files:rw']
            _name = str(job.id)
            '''
            ' The Docker SDK for Python expects the cpu_reservation value to be
            ' scaled to nanos (10^9). Because the job object contains unscaled
            ' (10^0) values, it must be conveted.
            '
            ' While the cpu_reservation value has to be in nanos, the
            ' mem_reservation value must be presented in an unscaled form
            ' (intuitive right?). Bacause the job object provides the memory
            ' value in megabytes, it is also necessary to convert the value.
            '''
            _resources = docker.types.Resources(
                cpu_reservation=job.n_cores * (10 ** 9),
                mem_reservation=job.mem_mb * (10 ** 6)
            )
            _restart_policy = docker.types.RestartPolicy(condition='none')
            '''
            ' Create the service with the prepared values.
            '
            ' Note: A service reserves hardware ressources. In case no worker
            '       node has the required ressources available (not reserved),
            '       the service gets queued by the Docker engine until a node
            '       is able to meet the requirements.
            '''
            service = client.services.create(
                _image,
                command=_command,
                constraints=_constraints,
                labels=_labels,
                mounts=_mounts,
                name=_name,
                resources=_resources,
                restart_policy=_restart_policy
            )
            job.status = 'scheduled'
        for job in jobs.filter(Job.status != 'complete',
                               Job.status != 'failed',
                               Job.status != 'submitted').all():
            try:
                service = client.services.get(str(job.id))
                job.status = service.tasks()[0].get('Status').get('State')
                if job.status == 'complete' or job.status == 'failed':
                    job.end_date = datetime.utcnow()
                    service.remove()
            except docker.errors.NotFound:
                job.status = 'failed'
        db.session.commit()